Influences of Environmental Temperature Changes on RF Phase and Beam-Energy Drift in the PLS 2.5-GeV Linac

The change in relative phase between the accelerating rf fields and the beam bunches is the dominant factor of beam-energy change in linear accelerators. Major factors of the changing rf phase are modulator high voltage jitters in the short term and drifts in environmental conditions in the long term. We have investigated influences of cooling water and air temperature changes on the rf phase and beam energy drifts in the PLS 2.5-GeV linear accelerator. In this article, we describe how the environmental factors change the beam energy drifts